One of the ways in which advertising works for us is that it provides us with a screen on which to play out our desires. It is not a matter of sense-making or story-telling as such -- the stories that advertisements tell us rarely amount to very much, let alone sense.

I have a haunting memory from when I was probably about four or five, of seeing a giant billboard for Ski yoghurt. The lush sky blue and the red of the strawberry were so tantalising that I felt it should be possible to eat the colours themselves. I often had that feeling about vivid colours -- that they should edible, or Oedipal. They promised more than they delivered, created a yearning for something quite beyond their ability to satisfy. This is not incidental to the issue at hand. To respond to an image with a desire to consume it, or consummate it, is to invest it with libidinal energy.

Now, for some reason, I was aware that although I wanted a yoghurt very much, I couldn't have one - whether because I was not allowed, or because there wasn't one, or for some other reason. I was yearning for something that I could not have. And none of the yoghurts I have obtained since, none of the thousands upon thousands of substitute yoghurts that have crammed my fridge week after week, have ever tasted as sublimely, wonderfully good, as the imaginary yoghurt I conjured up upon seeing the billboard.

Let me leave lingering to one side the question of how much this memory is in fact, and not in merely a punning sense, a 'screen memory' -- that is, a false memory construct which alludes to something that did happen and which I 'cannot' remember directly. What I'm interested in here is advertising technique, and the metonymy of desire.

The advertisement itself was minimal, reducible to a few basic elements. One could offer a quasi-Freudian reading of the 'oceanic bliss' evoked by the luscious blue, the sex organs alluded to by the juicy red berries, the orgasmic spill and splash of the creamy yoghurt, and so on. But that would be to miss the point, in a way. The basic colour scheme and the arrangement of minimal objects and words, invited any number of associations, but it did not 'contain' these specific associations -- any more than a Joan Miro painting 'contains' your interpretation of it.

The advertisement was designed to enable a certain dialectic of desire to be projected and played out on its canvas. The product -- or its signifier on the screen -- is supposed to occupy a certain abstract psychic space: the space of the object-cause of desire. Something you're lacking. Something you want, but can't have. Something that, even once you get it, is never actually the thing that you wanted, even if it gives you some satisfaction. So you keep searching, looking for the real thing.

It's the same whether it's yoghurts, sex or heroin: you keep chasing the dragon, looking for the real thing. Of course that thing doesn't really exist except as a gap, a hole in meaning, something which sets in motion the whole metonymic chain of wanting this yoghurt, that yoghurt, a different yoghurt, and so on. To put it another way, the point of advertising is to insert the signifier of its product into the space of the object-cause, and thus start off a chain of desire that can by definition never really be satisfied.

This is also the logic of our self-advertising (selfies) on social media, of course: we make of our own image, an image with which we have been scandalously and self-destructively besotted since infancy, an object-cause. Which is why one selfie is never enough, and one never really alights on the real thing, the ultimate selfie, the one that will finally do. It's also why people's selfies can be strangely addictive. As with Hello magazine, it's just a fellow mammal with interesting hair, but you always want to know if they'll finally get the perfect selfie, the sublime angle, the ultimate filter, that should-be-edible/Oedipal colour scheme.

Which is a way of saying that, unsurprisingly since social media are devised as marketing platforms, we have created a technology that is designed to multiply many times over, in compound fashion, the number of unsatisfied desires.